Equivalent & Substitute Parts for BK/MDA-3/4 Ceramic Fuse

Part Overview

The BK/MDA-3/4 is a 750 mA, 250 V AC ceramic cartridge fuse manufactured by Eaton - Electronics Division. This fuse is designed for use in 3AB and 3AG holders with dimensions of 1/4" x 1-1/4" (6.35mm x 31.75mm). The part is classified as obsolete, necessitating identification of active equivalent and substitute components to maintain circuit protection functionality in existing and new designs. Substitute parts must maintain identical current ratings, voltage ratings, package dimensions, and mechanical compatibility while meeting modern compliance standards.

Substiute Parts

BK/MDA-3/4

Eaton - Electronics DivisionIn Stock: 939BK/MDA-3/4 Datasheet

Current PartRFQ

BK/MDA-3/4-R

Eaton - Electronics DivisionIn Stock: 1093BK/MDA-3/4-R Datasheet

DirectRFQ

MDA-3/4-R

Eaton - Electronics DivisionIn Stock: 817MDA-3/4-R Datasheet

DirectRFQ

0326.750MXP

Littelfuse Inc.In Stock: 6490326.750MXP Datasheet

DirectRFQ

0326.750VXP

Littelfuse Inc.In Stock: 10450326.750VXP Datasheet

DirectRFQ

0326.750HXP

Littelfuse Inc.In Stock: 9860326.750HXP Datasheet

Parametric EquivalentRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the BK/MDA-3/4 is determined by strict equivalence in the following parameters:

• Current Rating: 750 mA (exact match required)
• Voltage Rating - AC: 250 V (exact match required)
• Package / Case: 3AB, 3AG, 1/4" x 1-1/4" (exact match required)
• Fuse Type: Cartridge, Ceramic (exact match required)
• Response Time: Slow Blow (exact match required)
• Mounting Type: Requires Holder (exact match required)

Substitute parts are grouped into two categories:

Direct Manufacturer Substitutes (Eaton - Electronics Division):

• BK/MDA-3/4-R
• MDA-3/4-R

These parts are manufactured by the original equipment manufacturer and maintain all critical electrical and mechanical parameters.

Parametric Equivalents (Littelfuse Inc.):

• 0326.750MXP
• 0326.750VXP
• 0326.750HXP

These parts are manufactured by Littelfuse Inc. and meet all mandatory electrical and mechanical specifications. They provide functional equivalence while offering enhanced compliance certifications and active product status.

Parameter Comparison

Engineering Selection Recommendations

For Direct Replacement (Same Manufacturer):

BK/MDA-3/4-R and MDA-3/4-R are the primary substitutes for the obsolete BK/MDA-3/4. Both parts are manufactured by Eaton - Electronics Division and maintain identical electrical and mechanical specifications. These parts carry active product status and provide enhanced compliance certifications including CE marking in addition to CSA and UL approvals. The transition from the obsolete BK/MDA-3/4 to either BK/MDA-3/4-R or MDA-3/4-R is direct with no design modifications required.

For Cross-Manufacturer Substitution:

The Littelfuse 326 series fuses (0326.750MXP, 0326.750VXP, 0326.750HXP) provide parametric equivalence for the BK/MDA-3/4. These parts meet all mandatory electrical and mechanical requirements: 750 mA current rating, 250 V AC voltage rating, 3AB/3AG package compatibility, and slow-blow response time. The Littelfuse parts offer enhanced breaking capacity (100A AC, 10kA DC versus 35A) and extended operating temperature range (-55°C to 125°C). All Littelfuse substitutes carry ROHS3 compliance and CE certification. Selection between Littelfuse models (0326.750MXP, 0326.750VXP, 0326.750HXP) is based on application-specific requirements, as all three maintain identical electrical and mechanical parameters.

Compliance Considerations:

The BK/MDA-3/4 is RoHS non-compliant. All substitute parts (both Eaton and Littelfuse) are ROHS3 compliant, meeting current environmental and regulatory requirements. Applications requiring CE marking certification should select from BK/MDA-3/4-R, MDA-3/4-R, or any Littelfuse 326 series equivalent, as the original BK/MDA-3/4 carries only CSA and UL approvals.

Frequently Asked Questions (FAQ)

Q: Can BK/MDA-3/4-R and MDA-3/4-R be used interchangeably with the obsolete BK/MDA-3/4?

A: Yes. Both BK/MDA-3/4-R and MDA-3/4-R are direct substitutes manufactured by Eaton - Electronics Division. They maintain identical current ratings (750 mA), voltage ratings (250 V AC), package dimensions (3AB, 3AG, 1/4" x 1-1/4"), and response characteristics (slow blow). No circuit modifications are required.

Q: What is the difference between the Eaton MDA-3/4-R and BK/MDA-3/4-R?

A: Both parts are manufactured by Eaton - Electronics Division and meet identical electrical and mechanical specifications. The primary difference is the part number designation. Both carry active product status and ROHS3 compliance. Selection between these two Eaton variants depends on internal inventory and procurement systems.

Q: Are Littelfuse 326 series fuses (0326.750MXP, 0326.750VXP, 0326.750HXP) compatible with the BK/MDA-3/4?

A: Yes. All three Littelfuse 326 series fuses are parametric equivalents. They maintain the required 750 mA current rating, 250 V AC voltage rating, 3AB/3AG package compatibility, and slow-blow response time. They are mechanically and electrically interchangeable with the BK/MDA-3/4 in standard circuit protection applications.

Q: What are the differences among the three Littelfuse 326 series models?

A: The three Littelfuse models (0326.750MXP, 0326.750VXP, 0326.750HXP) are parametrically identical. All three provide 750 mA current rating, 250 V AC / 125 V DC voltage ratings, 100A AC / 10kA DC breaking capacity, and -55°C to 125°C operating temperature range. Selection among these three models is based on application-specific requirements and availability, as electrical and mechanical performance is equivalent.

Q: Why do the Littelfuse substitutes specify 125 V DC rating while the original BK/MDA-3/4 does not?

A: The Littelfuse 326 series fuses provide enhanced DC voltage specifications (125 V DC) in addition to the 250 V AC rating. This additional specification does not affect AC-only applications. For applications requiring DC circuit protection, the Littelfuse substitutes offer expanded capability.

Q: What is the significance of the different Melting I²t values between parts?

A: Melting I²t is a thermal characteristic that affects fuse response time under specific fault conditions. The BK/MDA-3/4 has a Melting I²t of 7.8, while Eaton substitutes (BK/MDA-3/4-R, MDA-3/4-R) have 0.42, and Littelfuse substitutes have 7. These differences reflect manufacturing variations but do not affect the slow-blow response classification or 750 mA current rating. All parts maintain the same functional response time category.

Q: Are all substitute parts RoHS compliant?

A: Yes. All substitute parts listed (BK/MDA-3/4-R, MDA-3/4-R, 0326.750MXP, 0326.750VXP, 0326.750HXP) are ROHS3 compliant. The original BK/MDA-3/4 is RoHS non-compliant. For applications subject to RoHS requirements, any of the listed substitutes is appropriate.

Q: Do all substitute parts carry the same certifications as the original BK/MDA-3/4?

A: The original BK/MDA-3/4 carries CSA and UL approvals. All substitute parts carry CE, CSA, and UL approvals. The addition of CE certification on substitute parts represents enhanced compliance coverage and does not indicate reduced compatibility.

Q: Can I mix different substitute parts in the same circuit or equipment?

A: Yes. All listed substitute parts maintain identical electrical and mechanical specifications for the 750 mA, 250 V AC ceramic cartridge fuse category. They are mechanically and electrically interchangeable. However, for consistency in maintenance and inventory management, using a single substitute part number across an application is recommended.

Q: What holder types are compatible with these fuses?

A: All listed fuses require 3AB or 3AG holders. The fuse dimensions are standardized at 1/4" diameter x 1-1/4" length (6.35mm x 31.75mm). Existing holders compatible with the BK/MDA-3/4 will accept any of the listed substitute parts without modification.